This paper investigates the Fresnel diffraction of a monochromatic light beam due to annular square and circular apertures, when the system is focused in the Fresnel region. Perspective plots of the intensity distribution diagrams for modified Fresnel number(FMOD)=1, 2, . . . ; Lense focusing factor(FLNS)=1 and obstruction ratio(EPS)=0.01 are generated with IBM-370/168 computer. A comparison is done with the correspon-ding diagrams for unobstructed apertures. The results indicates that the central obstruction ratio(EPS=0.01) yields a systematic change in the shape of the intensity pattern over the image radius of a circular aperture. On the other hand the shape of the diffraction pattern remains unchanged for the square and the annular square apertures. It appears that the ring pattern generated with the annular circular aperture for FMOD=1, FLNS=1 and EPS=0.01 can effectively be used to drill good quality holes by using high power laser beam.